Single leg cycle training is superior to double leg cycling in improving the oxidative potential and metabolic profile of trained skeletal muscle
CR Abbiss, et. al. - Edith Cowan University
Single leg cycling may enhance the peripheral adaptations of skeletal muscle to a greater magnitude than double leg cycling. The purpose of the current study was to determine the influence of 3 wk high-intensity single leg and double leg cycle training on markers of oxidative potential and muscle metabolism and exercise performance. In a crossover design, nine trained cyclists (78 ± 7 kg, VO(2max): 59 ± 5 ml(.)kg(-1.)min(-1)) performed an incremental cycling test and a 16 km cycling time trial before and after 3 wk of double leg and counterweighted single leg cycle training (2 training sessions per wk). Training involved either 3 (double) or 6 (single) maximal 4 min intervals with 6 min recovery. Mean power output during the single leg intervals (198 ± 29W) was more than half that of the double leg intervals (344 ± 38W; P<0.05). Skeletal muscle biopsy samples obtained from the vastus lateralis revealed a training-induced increase in phosphorylated AMPKα(T172) for both groups (P<0.05). However, there was a greater increase in cytochrome c oxidase subunits II (COX II) and IV (COX IV) and GLUT-4 protein concentration following single compared with double leg cycling (P<0.05). Training-induced improvements in VO(2max):(3.9 ± 6.2% vs 0.6 ± 3.6%) and time trial performance (1.3 ± 0.5% vs 2.3 ± 4.2%) were similar following both interventions. We conclude that short-term high-intensity single leg cycle training can elicit greater enhancement in the metabolic and oxidative potential of skeletal muscle compared with traditional double leg cycling. Single leg cycling may therefore provide a valuable training stimulus for trained and clinical populations.
This study looks at isolated leg pedaling in a different way than what most think of isolated leg pedaling in that the other pedal is counterbalanced. From Jim Martin, the senior author of the study: "By adding a counterweight to one crank, you can pedal with one leg but with biomechanics that are similar to those during normal double leg cycling. Much different than you would do during non-counterweighted single leg cycling." This is closer to the "single-legged" condition PowerCranks puts on the athlete, in that all that is required when pedaling with two legs with PowerCranks is to fully unweight on the backstroke to keep the pedal going, similar to the requirements of this study.
The results really support the benefits of this kind of isolated leg training. Not only were the athletes able to generate substantially more wattage one legged than would be expected taking half of the two legged interval power (25 watts - indicating, most likely, improved efficiency and utilization of more muscle mass) but other metabolic changes indicated this to be a more effective way of training cycling musculature. Even though overall improvements were not seen in this study, as the senior author has stated about this study: "While it is true that we did not obtain a performance improvement we did not really expect it after only 6 total workouts over three weeks. Anytime you design a study you are constrained by what you believe the participants are will to do and how much time they will take off of their normal training. We decided on three weeks knowing it might not improve performance. That's where the analysis of muscle biopsies came in. We pulled biopsies before and after each block of training (single and double) and analyzed the tissue. The results for increases in glut-4 (insulin and contraction mediated glucose transporter) and CoxII and CoxIV (limiting steps in the respiratory chain) are highly compelling. They suggest that this will be a potent training stimulus as well as clinical modality."
There are only two problems with single-legged training. 1. It takes twice as long to train both legs equally. 2. It doesn't train the two-legged coordination. Using PowerCranks as your single-legged training facilitator solves both problems because both legs are being trained at the same time and it is training the two legged coordination at the same time. No wonder PowerCranks are such a powerful tool.
Link to study: PubMed